Study of the binding of adenosine to chemically and photochemically modified polyuridylic acids, and of guanosine to chemically and photochemically modified polycytidylic acids. Study of energy transfer between thymine, uracil and cytosine and suitable fluorescent acceptors; this includes intramolecular energy transfer in molecules incorporating the pyrimidine and the acceptor at the ends of a covalently-bonded polymethylene chain. Studies of pyrimidine photochemistry, including the photochemistry of new substituted pyrimidines and new photoproducts from known substituted pyrimidines.